[{"_id":1,"borough":"Brooklyn","reviews":[]}]

db.collection.update({borough:"Brooklyn"},{$push:{"reviews":{$each:[{"name":"Frank Zappa","date":"January 3, 2019","rating":3,"comments":"This restaurant is not good"},{"name":"Freddie Mercury","date":"January 3, 2019","rating":5,"comments":"This restaurant is my favorite"}]}}})